Yes, releasing a creatu to the forest gets it off your own account, but the creatu doesn't disappear. It loses its name and then waits in limbo for someone to adopt it. (As an aside, I just recently learned that when you hatch a creatu and release it instead of naming it, it goes to the forest instead of disappearing from the game!)
Kir is a good way to delete the extra creatu in this game entirely/permanently. It is necessary for there to be ways to permanently siphon off some of the excess creatu, because it helps to maintain a balance in the game. If no creatu were ever truly destroyed, their values would plummet because the market would be totally saturated. This would make it impossible to sell creatu, and harder to make tu.
There are only a few true ways to delete creatu that I know of: Kir quests, Creatu Collections, Seasonal events where you turn in specific creatu (like the Xisters), and Shrines. (There might be more but those are all I can think of at the moment.)
Anyway, if anything I think we need more ways to make creatu completely disappear, to make sure that the demand for them continues. Especially the common ones. Even though getting 0 points is annoying, it is random, and something that everyone has to do if they play Kir quest, so it keeps it fair. I think of it like a tax that must be paid to keep the Res economy functioning well.
I do agree there should be more recognition for accomplishing more Kir quests beyond round 3, level 120 though. Starting with letting the numbers continue to climb at the very least.